Waterbed heaters typically consist of solid resistance wires or etched aluminum resistance elements which have been embedded or imprinted in a flat flexible mylar mat and sealed in a protective PVC sheath. Generally, the resistance elements are laid out in a serpentine pattern throughout the mat. These waterbed heaters are provided to heat and maintain the liquid in the flotation mattresses at a desired temperature.
Typically, waterbed heaters are arranged in flat engagement between the mattress support platform of the waterbed, and the bottom wall of the liquid filled bladder which forms the mattress. A control is provided to manually adjust the temperature of the liquid in the mattress, utilizing a small temperature sensing device, such as a thermocouple or thermistor, at the free end of a thin elongated flexible conductor. The conductors extend from the control unit between the bed platform and a mattress to locate the temperature sensor in engagement with the mattress spaced from the heater.
While temperature control is a continuous concern with waterbeds, temperature control also is an important aspect of conventional beds, and other fluid filled mattresses, such as air beds. Similarly, the temperature control for any of these types of beds need not be necessarily located between the bed support and the fluid filled mattress, but may be located on top of the mattress, between the bed occupant, and the mattress. An effective apparatus for accomplishing this type of heater utilizes a pillow top assembly connected to the top surface of the mattress. The heating unit may then be embedded within the pillow top assembly, or connected to the upper or lower surface of the pillow top assembly, to provide warmth to the bed occupant on top of the pillow top assembly.
Sleep research shows that a warm bed can promote sleep efficiency. However, body heat of the bed occupant will raise the bed temperature. This raise in bed temperature is typically not detected by conventional thermostats on conventional heating apparatus. If the bed temperature is too warm, undesirable sleep stage changes may occur.
One stage of sleep is identified as REM (rapid eye movement) sleep. An increased bed temperature cannot only be uncomfortable, but can cause the body core temperature of the occupant to increase during REM sleep, because the human body does not regulate body temperature during REM sleep.
Studies also indicate that selective application of heat in various areas of the bed occupant's body can affect blood flow, core body temperature, sleep staging, and other physiological conditions, both negatively and positively. It is therefore important to control the temperature in these regions. For example, some types of diseases will render body appendages insensitive to heat. Unheated, or reduced heat zones are typically necessary for these types of users.
In addition to control of temperature of the bed, it would be desired to detect the presence of an occupant in the bed. An occupant sensor would detect the presence of a person in the bed, and adjust the bed temperature accordingly. Occupant sensors could also be used for a wide variety of other operations, including the control of various devices about the home, air chambers adjustments (for air beds), various safety alarms, and other controls.